Nope, definitely not big enough for any tang! "Dori" needs at least a 6ft long tank (180g is the minimum recommended size), and a yellow tang needs at least a 4ft long tank (recommended size is actually 125g, which is 6ft long, but many people have kept them in 90g tanks with success). You are actually going to be quite limited in what you can keep, especially since a hexagonal tank doesn't offer much vertical swimming room. I would look for fish that don't need anything more than a 20-30g tank minimum. Live Aquaria.com is a very reputable site that will give you good info on tank size minimums. Welcome!